Ein Plädoyer für Banken-Vielfalt

Das deutsche Bankensystem ruht seit Jahrzehnten auf drei Säulen: den privaten Kreditbanken, den öffentlichen Banken des Sparkassensystems und den genossenschaftlichen Banken. Das Drei-Säulen-System scheint ursächlich für die Stabilität im deutschen Bankensystem zu sein. Gerade die Krise hat gezeigt, dass es für ein Bankensystem vorteilhaft ist, wenn es darin nicht nur einen Typus von Banken gibt. Wir müssen eine Pluralität von Organisationsformen im Bankwesen erhalten und weiterentwickeln

Shape from shading from images rendered with various surface types and light fields

Shape constancy is referred to as the tendency for the perceived shape of an object to remain unchanged even under changed viewing and illumination conditions. We investigated, in two experiments, whether shape constancy would hold for images of 3-D solid objects defined by shading only, whose renderings differed in terms of surface material type (bi-directional reflectance distribution functions), light field, light direction, shape, and specularity. Observers were presented with the image of a sphere or an ellipsoid and required to set perceived orientation and cross-section profile on designated points of the image. Results showed that shape judgments varied with all the aforementioned variables except specularity. Shape estimates were more precise with specular than asperity scattering surfaces, collimated than hemispherical diffuse lighting conditions, lower than higher elevations, spherical than ellipsoidal shapes, but not different between surfaces having differing specularity. These results suggest that shape judgments are made largely on the basis of the overall intensity distribution of shading, and that the portions of intensity distribution that are due to nonstructural variables such as surface material type or light field are not excluded in the process of shape estimation, as if being due to structural components. It is concluded that little constancy is expected in the perception of shape from shading

Perception of illumination direction in images of 3-D convex objects:Influence of surface materials and light fields

Shading of 3-D objects refers to variations in luminance or color as a function of the angle of the illumination direction with respect to the surface. Shading gives rise to a compelling sense of shape, illumination conditions and surface properties. However, it is not yet certain how this is achieved. We used an illuminant direction matching procedure to examine how well human observers can estimate the direction of illumination in images of rotating 3-D geometrical shapes in different light fields. Stimuli were renderings of a dodecahedron and a sphere projected orthographically and juxtaposed on a CRT screen. Two lighting modes (collimated and hemispherical diffuse lighting), twenty-six illuminant directions (differing in azimuth and elevation) and perfectly diffuse reflectance with albedo 0.5 were used to render the faces of the two stimuli. Since the two shapes were convex and situated in empty space, neither interreflection nor cast shadow was produced. At the start of each trial, the two stimuli were presented with different directions of illumination. Observers adjusted the direction of illumination on the sphere to match the direction of illumination on the dodecahedron. Results revealed no systematic difference in matched directions between the two lighting conditions, neither in azimuth nor in elevation. This suggests that in the absence of cast shadow, observers may use the location of the brightest point as a cue to the direction of illumination. Although the appearance of image shading can be appreciably changed under different lighting conditions, for the case of Lambertian reflectance, the peak in the luminance distribution remains fixed